It is known that integrated circuits are generally provided with terminals for external control signals which allow one to enable/disable the integrated circuits, or some circuit blocks thereof, for example in order to put the integrated circuits in a low power consumption mode ("stand-by"), or in order to allow that shared resources of an electronic system are assigned to different integrated circuits.
For example, in memory devices, and particularly in the non-volatile ones such as ROMs, EPROMs, EEPROMs and Flash EEPROMs, two control terminals are generally provided: a terminal for enabling the whole device (universally named CEn), and a terminal for enabling the output data buffers (named OEn). The former is used to put the whole device in said low power consumption operating mode (stand-by), and the latter is used to put the output data buffers in a high output impedance condition, so that an external data bus can be assigned to other devices which share the same.
It is also known that one of the most important aspects of integrated circuits design, and particularly of memory devices, is that related to noise affecting the supply and reference voltages. In the case of memory devices, with the increase of their speed and the number of output data lines, the output data buffers switching at the end of a read operation to transfer the read data to the external data bus cause variations of the supply and reference voltage levels. In fact, due to the current sunk by the output data buffers the supply voltage falls below its nominal value, and the reference voltage rises over its nominal value.
This affects the logic levels of the control signals which are supplied to the control terminals of the integrated circuit, and undesired disabling of the output data buffers or even of the whole integrated circuits can occur. This obviously compromises the correct working of the integrated circuit in the electronic system to which it belongs.